fix(frontend): send drive uploads as multipart instead of JSON

[mmabrouk]

Dragging a file (or using the Upload button, or committing staged files) in the agent chat's Files drawer fails with 422 {"detail":[{"type":"missing","loc":["body","file"],"msg":"Field required"}]}. The request goes out as Content-Type: application/json with body {"file":{}}.

Before: uploadMountFile posts its FormData through the shared axios instance, whose default application/json content type makes axios 1.x JSON-serialize the FormData (formDataToJSON), collapsing the File to an empty object. Every upload affordance in the drawer funnels into this one helper, so all of them fail. The surface shipped dark behind NEXT_PUBLIC_AGENT_FILE_UPLOADS, which is why nobody hit it until the flag came on in dev.
After: the post carries an explicit Content-Type: multipart/form-data, the same fix and comment the composer's attachment transport uses for the identical trap.

Verified against v0.106.2/main: the reworked drawer still funnels into this unchanged helper, so the one-line fix applies cleanly.

Not fixed here, filed separately: dropping a folder additionally arrives as a single zero-byte pseudo-file because the drop handlers read dataTransfer.files with no directory enumeration; that fix needs authoring against the reworked drawer on main.

https://claude.ai/code/session_01A1XQVjHPYJgVBHWSNUphtx

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Project	Deployment	Actions	Updated (UTC)
agenta-documentation	Ready	Preview	Aug 1, 2026 4:48pm

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📝 Walkthrough

Summary by CodeRabbit

• Bug Fixes
  • Fixed file uploads from mounted drives by ensuring multipart form data is transmitted correctly.

Walkthrough

The drive media upload request now sets multipart/form-data explicitly. This prevents the shared JSON content type from handling the FormData payload incorrectly.

Changes

Drive media upload

Layer / File(s)	Summary
Multipart upload request web/oss/src/components/Drives/driveMedia.ts	uploadMountFile now declares the multipart/form-data content type in its Axios request.

Estimated code review effort: 2 (Simple) | ~5 minutes

Possibly related issues

• (bug) Dropping a folder into the Files drawer uploads a zero-byte pseudo-file instead of the folder's contents #5626: Addresses folder-drop handling in the same Files drawer upload flow.

Possibly related PRs

• Agenta-AI/agenta#5459: Introduced uploadMountFile, which this change updates.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly and concisely describes the main change: sending frontend drive uploads as multipart instead of JSON.
Description check	✅ Passed	The description directly explains the upload failure, root cause, fix, verification, and folder-drop scope.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/drive-upload-multipart

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[github-actions]

Railway Preview Environment

Status	Destroyed (PR closed)

Updated at 2026-08-01T18:17:16.219Z